1. Field of the Invention
This invention relates to an improved underwater truss structure, and more particularly to an improved underwater truss structure wherein rods of an underwater truss including a large number of mutually nonparallel rods are provided with plate-like structural members (hereinafter "brims") having surfaces orthogonal to the rods.
2. Description of the Related Art
The present inventor earlier invented a fluid-interference structure utilizing an underwater truss that can be used as a marine structure in place of conventional concrete-caisson breakwaters, tetrapods and other such structures that rely on weight. This is a light-weight marine structure composed of units of uniform, easy-to-handle size. It can be mass-produced as a standardized product at low cost and is usable even on ground that is too weak for use of a conventional structure. The basic structure is described in Japanese Patent Publication No. 58(1983)-26443 and various improved structures are disclosed in, for example, Japanese Unexamined Patent Publication No. 63(1988)-247413, Japanese Unexamined Utility Model Publication No. 1(1989)-180530, Japanese Unexamined Patent Publication No. 2(1990)-70812, Japanese Unexamined Patent Publication No. 6(1994)-136727, Japanese Unexamined Patent Publication No. 6(1994)-264423, Japanese Unexamined Patent Publication No. 6(1994)-280234 and Japanese Unexamined Patent Publication No. 8(1996)-105030.
The basic structural unit of the underwater truss structure consists of a planar skeleton composed of rods and spheres assembled in planar interconnection and a three-dimensional skeleton of an interconnected regular triangular pyramid and a regular square pyramid. One of the disclosed structures is provided with plate-like brims having surfaces orthogonal to the rods. Basically, this underwater truss structure operates by utilizing the interference between a fluid passing through the interior of the structure and the shape of the structure to agitate the motion of the fluid and convert it into a turbulent flow. Providing disk-like brims on the rods markedly increases the contact area with the fluid per unit volume. Since this increases the capability of the structure to interfere with fluid motion, the underwater truss structure with brims is immensely more cost-effective than conventional marine structures.
The underwater truss structure with brims can provide a considerable interference effect in the case of a wave component having high kinetic energy per spatial unit. Still, irrespective of this and its ability simply to interfere with a large wave to give it a desired waveform, it cannot totally eradicate waveforms and therefore cannot perform sufficiently as a practical breakwater structure.
The underwater truss structure with brims can, however, be effectively utilized for systematically converting waves, tides, currents and other types of fluid motion into turbulent flow and eddies and/or into the microdisturbed state. Owing to its relatively light weight, moreover, the structure has the potential for practical application at low cost from the viewpoint of production, assembly and installation. Taking actual needs in coastal waters into account, therefore, it is desirable to pursue its further development toward enabling use of the sea's kinetic energy in diverse ways.
Specifically, the kinetic energy of ocean waves is potentially utilizable for various purposes, such as to improve water quality by increasing dissolved oxygen and to enhance the amount of deep-region nutrient salts conducted to and mixed with water in the photic region for instance, in order to create an environment for adherence of useful plant life. The structure should therefore desirably be improved to have control capabilities enabling such uses of wave energy in costal waters.